The present invention relates generally to improvements in fastener driving tools, and specifically to such tools which are combustion powered and are used in rough framing and/or the installation of trim, other decorative applications and finishing applications utilizing fasteners which are relatively small, made of relatively thin wire stock, and/or which are used with relatively small and/or delicate workpieces. The latter will generally be referred to as xe2x80x9ctrim applications.xe2x80x9d Included in the present tool are several features intended to make the manufacture, use and/or repair of such tools more efficient.
Portable combustion powered tools for use in driving fasteners into workpieces are described in commonly assigned patents to Nikolich, U.S. Pat. Nos. Re. 32,452; 4,403,722; 4,483,473; 4,483,474; 4,552,162; 5,197,646 and 5,263,439, all of which are incorporated herein by reference. Such combustion powered tools particularly designed for trim applications are disclosed in commonly assigned U.S. Pat. No. 6,016,622, also incorporated by reference herein. Similar combustion powered nail and staple driving tools are available from ITW-Paslode under the IMPULSE(copyright) brand.
Such tools incorporate a generally pistol-shaped tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas also called a fuel cell. A battery-powered high voltage spark unit, also known as an electronic power distribution unit or electronic sending unit produces the spark for ignition, and a fan located in the combustion chamber provides for both an efficient combustion within the chamber, and facilitates scavenging, including the exhaust of combustion by-products. The engine includes a reciprocating piston having an elongate, rigid driver blade disposed within a piston chamber of a cylinder body.
A wall of the combustion chamber is axially reciprocable about a valve sleeve and, through a linkage, moves to close the combustion chamber when a workpiece contact element (WCE) at the end of a nosepiece, or nosepiece assembly, connected to the linkage is pressed against a workpiece. This pressing action also triggers the introduction of a specified volume of fuel gas into the combustion chamber from the fuel cell.
Upon the pulling of a trigger, which causes the ignition of the gas in the combustion chamber, the piston and the driver blade are shot downward to impact a positioned fastener and drive it into the workpiece. As the piston is driven downward, a displacement volume enclosed in the piston chamber below the piston is forced to exit through one or more exit ports provided at a lower end of the cylinder. After impact, the piston then returns to its original or xe2x80x9creadyxe2x80x9d position through differential gas pressures within the cylinder. Fasteners are fed into the nosepiece from a supply assembly, such as a magazine, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
To prevent firing of the tool prior to the WCE being pressed against a workpiece, it is known to provide a separate actuator switch which is triggered by movement of the WCE and which is also electrically connected to the trigger switch. The circuit is designed so that the trigger switch is inoperable until the actuator switch is activated by movement of the WCE. In prior tools, the mechanical linkage of such actuation systems involved multiple components that complicated manufacture and assembly of the tools.
Another design feature of such tools is that the actuator and trigger switches are remotely mounted in the tool housing, thus complicating assembly and manufacture. In addition, the construction of the switches was such that internal optical components were difficult to maintain in alignment. Further, the switches were prone to foreign matter falling on the optics and impairing operation.
Thus, a first object of the present invention is to provide an improved integrated spark unit for a combustion powered tool in which the actuator and trigger switches are mounted on a single circuit board with the spark unit.
Another object of the present invention is to provide an improved combustion powered tool in which the actuator switch and the trigger switch are provided in a single unit in close proximity to each other.
Still another object of the present invention is to provide an improved integrated spark unit for a combustion powered tool in which the actuator is unitary for facilitating manufacture, assembly and operation.
Yet another object of the present invention is to provide an improved combustion powered tool in which the actuator and trigger switches are provided in a single molded unit which also provides the mounting point for a unitary switch actuator, the latter configured for being engaged by movement of the workpiece contact element to enable actuation of the trigger switch.
The above-listed objects are met or exceeded by the present combustion powered tool featuring an integrated spark unit having the actuator and trigger switches mounted together on a common circuit board with the spark supply and also with the switches being molded together for easier manufacturing and assembly. A preferably unitary actuator is mountable at one end to the switch unit and a second movable end is actuated by movement of the workpiece contact element to activate the actuator switch and thus enable the actuation of the trigger switch for tool firing. The actuator accommodates overtravel of the combustion chamber due to workpiece contact element movement.
More specifically, an integrated spark unit is provided for a combustion-powered tool having a workpiece contacting element which moves relative to the tool as the tool is depressed prior to firing. The unit includes a high voltage spark supply for providing an ignition spark, a unitary printed circuit board having a first portion configured for receiving and being electrically connected to the high voltage spark supply and a second portion configured for receiving and being electrically connected to both an actuator switch and a trigger switch. The trigger switch, the actuator switch and the spark supply being electrically connected so that to enable firing, the workpiece contact element actuates the actuator switch, which then enables the activation of the trigger switch. A preferably unitary actuator has a fixed end, a movable end engageable by movement of the workpiece contact element and a middle portion for engaging the actuator switch upon movement of the movable end caused by depression of the tool against a workpiece.